1. Field of the Invention
The present invention relates to an image input apparatus and, more particularly, to an image input apparatus for illuminating a mail item by an illuminating light source and inputting an image of the illuminated portion in order to sort the mail items by image recognition.
2. Description of the Related Art
Conventionally, as the above-mentioned image input apparatus, there has been provided an apparatus for sorting mail items which are generally called flat mails, (referred to as a flat mail sorter, hereinafter). The size of flat mail is maximum 50 mm in thickness, 400 mm in length, and 300 mm in width, roughly. The flat mail sorter captures an image of a flat mail surface by the image input apparatus, reads a written address by a recognition processing unit existing at the post stage, and sorts and accommodates the mails into a sorting box in which the mail is sorted by district in accordance with the reading result.
The flat mail has physical features that the thickness of the flat mail has a wider range, the lateral width thereof is wider, and the like, as compared with those of a letter (post card, or standard-size mail item, etc.). Therefore, the illumination for the image input requires linear illumination having a wider irradiating-width and a deeper irradiating-depth. This results in necessitating an illuminating light source having a high illuminance and results in generating a large amount of heat.
Since a high output lamp is used for the above reasons in the image input apparatus, an infrared light component of the illuminating light source makes an illuminating window glass, through which irradiated light is transmitted, apt to have a high temperature. As a result, problems readily occur such that light distribution of the illuminating light is degraded and made non-uniform by dust burned onto the window glass, which is generated by mail conveyance, etc., thereby degrading image quality and diminishing sorting performance. This requires frequent maintenance, such as cleaning the illuminating window glass every day. Consequently, for purpose of improvement in maintenance performance, it is necessary to suppress an increase in temperature of the illuminating window glass and decrease dirty region due to the burned dust.
It is necessary to cool the apparatus up to about room temperature before starting a lamp exchanging operation, when lamp burnout occurs. It takes a long time to cool the apparatus due to the usage of the high output lamp on the basis of the above reason, thereby interrupting the operation on the apparatus during the cooling time.
To solve the problems, for example, U.S. Pat. No. 5,814,802 disclosed an image input apparatus for carrying, along a conveyor, a flat mail onto which a bar code label is put, illuminating the flat mail from the upper side, and detecting an image of the bar code label by a CCD camera, wherein heatsink fins are mounted to a surface on the upper side of a reflective mirror provided in the illuminating means to cover the upper portion of a lamp in the illuminating means, and the illuminating means is cooled by a laminar air flow which flows across the upper portion of the heatsink fins and is exhausted to the outside. However, in this conventional image input apparatus, the heat removal is also insufficiently effected in an area on the conveyor side of the illuminating means and the illuminating window glass is apt to have a high temperature.
It is an object of the present invention to provide an image input apparatus for a mail item having an illuminating apparatus in which it is difficult for a foreign matter to be burned onto a glass illumination window even if mail items are contacted thereto for a long time. This makes the maintenance simple, and the reliability is excellent.
According to the present invention, there is provided an image input apparatus comprising: illuminating means for irradiating light to an object which conveying means moves in a predetermined direction; image pickup means for picking up an image of the object in a image pickup field; and air cooling means for cooling the illuminating means, wherein the illuminating means has a plurality of window glasses for transmitting irradiated light, among which the outermost window glass is a heat ray transmitting glass and an internal window glass is a heat ray absorbing glass, and the heat ray absorbing glass is forcedly cooled in the front surface and the rear surface thereof by an air flow generated by the air cooling means.
According to the present invention, the internal heat ray absorbing glass absorbs a heat dissipating energy from a light source, and the forced air-cooling operation causes the temperature of the heat ray absorbing glass to decrease, thereby reducing secondary dissipation of a heat dissipating energy from the glass itself as much as possible. The outermost window glass is set to the heat ray transmitting glass. As a consequence, it is capable of preventing the temperature increase of the outermost glass that is caused by the heat dissipating energy, and it is difficult that a foreign matter is burn to the window glass for illumination if being adhered thereto for long time. This makes the maintenance simple, and the reliability to the image input apparatus can be improved.